Nonwoven web structures are generally produced using three basic processes: (1) spunbonding, where continuous filaments are extruded and deposited on a screen to form a continuous nonwoven structure; (2) meltblowing, where the extruded polymer melt is stretched, broken into short fibers, blown by a jet of heated air, and deposited on a belt to form the nonwoven structure; and (3) carding, where staple fibers are separated by a carding machine and laid out in a nonwoven web structure.
Nonwoven materials are commonly used in the manufacture of protective garments such as those worn by medical personnel, clean room personnel, and farm workers. For example, U.S. Pat. No. 4,196,245 describes a composite nonwoven fabric for use in disposable surgical items that comprises at least two hydrophobic plies of microfine fibers of a fiber diameter of up to about 10 microns, and at least one nonwoven cover ply. U.S. Pat. No. 4,508,113 discloses a water impervious laminated material comprising a three-ply hydrophobic microfine fiber structure sandwiched between and fuse-bonded to two layers of conjugate fibers having a low melting sheath and a high melting core. U.S. Pat. No. 4,555,811 describes a water impervious microfine fiber laminated material for use in making disposable operating room gowns and comprising an inner creped hydrophobic microfine fiber structure sandwiched between and bonded to two reinforcing layers of nonwoven fibers. U.S. Pat. No. 5,108,827 discloses a thermally-bonded nonwoven fabric that is made from a web comprising 100 to 5 weight percent multiconstituent fibers. The fibers are made from a dispersion of two or more polymers that can be melt spun into fibers and then formed into webs, e.g., by carding, airlaying, or wetlaying. Biconstituent staple fibers made from a blend of ethylene/1-octene and polypropylene can be used.
Nonwoven materials to be used in the manufacture of such protective garments have two essential requirements: liquid barrier properties, and comfort to the wearer. Most of the liquid barrier fabrics currently available exhibit very low air permeability, causing heat build-up and therefore heat stress for the garment wearer. Some currently available fabrics such as spunbonded materials provide adequate air flow, but lack the required liquid barrier properties. There is a need for a nonwoven material that exhibits a combination of impermeability to liquids and high air permeability.